1 POWER PLANTS INSTRUCTOR’S MANUAL UET DEPARTMENT OF MECHANICAL ENGINEERING (KSK CAMPUS) UNIVERSITY OF ENGINEERING & SCIENCE TECHNOLOGY LAHORE Prepared By: Mr. Attique Arshad
1
POWER PLANTS INSTRUCTOR’S MANUAL
UET
DEPARTMENT OF MECHANICAL
ENGINEERING (KSK CAMPUS) UNIVERSITY OF ENGINEERING & SCIENCE TECHNOLOGY
LAHORE
Prepared By: Mr. Attique Arshad
2
Table of Contents 1. Experiment No -1 ............................................................................................................... 8
1.1 Objective ..................................................................................................................... 8
1.2 Steam turbine power plant........................................................................................... 8
1.2.1 Basic Process ....................................................................................................... 8
1.2.2 Types of steam turbine power plants based on efficiency improvements ........... 9
1.2.3 Components ....................................................................................................... 12
2. Experiment No -2 ............................................................................................................. 14
2.1 Objective ................................................................................................................... 14
2.2 Apparatus .................................................................................................................. 14
2.3 Theory ....................................................................................................................... 14
2.3.1 Boiler.................................................................................................................. 14
2.4 Specification .............................................................................................................. 22
2.5 Procedure ................................................................................................................... 22
2.5.1 Boiler Starting up ............................................................................................... 22
2.6 Specimen Calculation ................................................................................................ 23
2.7 Observations .............................................................................................................. 23
2.8 Comments.................................................................. Error! Bookmark not defined.
3. Experiment No – 3 ........................................................................................................... 25
3.1 Objective ................................................................................................................... 25
3.2 Apparatus .................................................................................................................. 25
3.3 Theory ....................................................................................................................... 25
3.3.1 Dryness fraction/ quality of steam ..................................................................... 25
3.3.2 Throttling process & throttling calorimeter ....................................................... 25
3.4 Specifications ............................................................................................................ 26
3.5 Procedure ................................................................................................................... 26
3.6 Specimen Calculation ................................................................................................ 26
3.7 Observations .............................................................................................................. 27
3.8 Comments.................................................................. Error! Bookmark not defined.
4. Experiment No - 4 ............................................................................................................ 28
4.1 Objective ................................................................................................................... 28
4.2 Apparatus .................................................................................................................. 28
4.3 Theory ....................................................................................................................... 28
4.3.1 Superheater ........................................................................................................ 28
4.4 Specifications ............................................................................................................ 31
4.5 Procedure ................................................................................................................... 31
4.6 Calculations ............................................................................................................... 31
3
4.7 Observations .............................................................................................................. 31
4.8 Comments.................................................................. Error! Bookmark not defined.
5. Experiment No – 5 ........................................................................................................... 32
5.1 Objective ................................................................................................................... 32
5.2 Apparatus .................................................................................................................. 32
5.3 Theory ....................................................................................................................... 32
5.3.1 Steam turbine ..................................................................................................... 32
5.4 Specification .............................................................................................................. 35
5.5 Procedure ................................................................................................................... 35
5.6 Specimen Calculation ................................................................................................ 35
5.7 Observations .............................................................................................................. 36
5.8 Comments.................................................................. Error! Bookmark not defined.
6. Experiment No - 6 ............................................................................................................ 37
6.1 Objective ................................................................................................................... 37
6.2 Apparatus .................................................................................................................. 37
6.3 Theory ....................................................................................................................... 37
6.3.1 Condenser .......................................................................................................... 37
6.4 Specification .............................................................................................................. 40
6.5 Procedure ................................................................................................................... 40
6.6 Observations .............................................................................................................. 40
6.7 Comments.................................................................. Error! Bookmark not defined.
7. Experiment No –7 ............................................................................................................ 41
7.1 Objective ................................................................................................................... 41
7.2 Apparatus .................................................................................................................. 41
7.3 Theory ....................................................................................................................... 41
7.3.1 Basic Process in a steam power plant ................................................................ 41
7.3.2 Basic components of a steam power plant ......................................................... 41
7.3.3 Overall efficiency of steam power plant ............................................................ 42
7.3.4 Efficiency improvement..................................................................................... 42
7.4 Specifications ............................................................................................................ 44
7.5 Specimen Calculation ................................................................................................ 44
7.6 Observations .............................................................................................................. 44
7.7 Comments.................................................................. Error! Bookmark not defined.
8. Experiment No – 8 ........................................................................................................... 45
8.1 Objective ................................................................................................................... 45
8.2 Apparatus .................................................................................................................. 45
8.3 Theory ....................................................................................................................... 45
4
8.3.1 Natural gas engine.............................................................................................. 45
8.3.2 Turbocharger ...................................................................................................... 46
8.3.3 Aftercooler ......................................................................................................... 46
8.3.4 Firing order of the engine .................................................................................. 47
8.3.5 Heat exchangers ................................................................................................. 47
8.4 Specifications ............................................................................................................ 48
8.4.1 Engine specifications ......................................................................................... 48
8.4.2 Alternator specifications .................................................................................... 48
8.5 Specimen Calculation ................................................................................................ 48
8.6 Observations .............................................................................................................. 48
8.7 Comments.................................................................. Error! Bookmark not defined.
9. Experiment No – 9 ........................................................................................................... 50
9.1 Objective ................................................................................................................... 50
9.2 Apparatus .................................................................................................................. 50
9.3 Theory ....................................................................................................................... 50
9.3.1 Diesel engine ...................................................................................................... 50
9.3.2 Turbocharger ...................................................................................................... 51
9.3.3 Engine cooling system ....................................................................................... 51
9.3.4 Diesel fuel injection system ............................................................................... 52
9.4 Specifications ............................................................................................................ 52
9.5 Specimen Calculation ................................................................................................ 53
9.6 Observations .............................................................................................................. 53
9.7 Comments.................................................................. Error! Bookmark not defined.
10. Experiment No –10 ....................................................................................................... 54
10.1 Objective ................................................................................................................ 54
10.2 Apparatus ............................................................................................................... 54
10.3 Theory .................................................................................................................... 54
10.3.1 Cooling tower..................................................................................................... 54
10.3.2 Working of Cooling towers ............................................................................... 54
10.3.3 Types of cooling towers ..................................................................................... 54
10.4 Specimen Calculation ............................................................................................ 56
10.5 Theoretical Cooling ............................................................................................... 56
10.6 Actual cooling........................................................................................................ 56
10.7 Observations .......................................................................................................... 56
10.8 Comments .............................................................. Error! Bookmark not defined.
5
List of Figures Fig.1. 1. Steam turbine power plant running on kerosene oil .................................................... 8 Fig.1. 2. T-s diagram of simple Rankine cycle .......................................................................... 9
Fig.1. 3. Effect of heating the steam to a higher temperature at the turbine inlet ..................... 9 Fig.1. 4. Schematic diagram of a superheater .......................................................................... 10 Fig.1. 5. Rankine cycle with reheating of the steam ................................................................ 10 Fig.1. 6. Schematic diagram of the steam power plant with a reheater ................................... 11 Fig.1. 7. Schematic of steam power plant with regeneration using open feedwater heater and
its T-s cycle .............................................................................................................................. 11 Fig.1.8. Schematic diagram of steam power plant with regeneration using closed feedwater
heater and its T-s cycle ............................................................................................................ 12 Fig.1. 9. Components of a steam turbine power plant ............................................................. 12
Fig.2. 1. Schematic of a water tube boiler ............................................................................... 15 Fig.2. 2. Schematic of a fire tube boiler .................................................................................. 15
Fig.2. 3. Forced water circulation vs natural water circulation in a boiler .............................. 16 Fig.2. 4. A stationary boiler ..................................................................................................... 16
Fig.2. 5. A portable boiler ........................................................................................................ 17 Fig.2. 6. Use of the boiler in locomotive ................................................................................. 17
Fig.2. 7. Schematic diagram of the boilers under operation in a ship ..................................... 18 Fig.2. 8. A boiler in horizontal position................................................................................... 18 Fig.2. 9. A boiler with inclined water tubes ............................................................................ 18
Fig.2. 10. A boiler with vertical fire tubes ............................................................................... 19
Fig.2. 11. Schematic of internally fired boiler on left side vs externally fired boiler on right
side ........................................................................................................................................... 19 Fig.2. 12. T-s diagram of supercritical and subcritical Rankine cycle .................................... 20
Fig.2. 13. Boiler running on pulverized coal ........................................................................... 21 Fig.2. 14. Steam cycle with supercharged boiler ..................................................................... 21
Fig.2. 15. Boiler using fluidized bed of coal and limestone for steam production .................. 22
Fig.3. 1. Schematic of a throttling calorimeter ........................................................................ 25
Fig.3. 2. Throttling process on t-s and h-s chart ...................................................................... 26
Fig.4. 1. Schematic diagram of a superheater present inside boiler ........................................ 28 Fig.4. 2. Schematic diagram of a superheater with separate fuel supply................................. 28
Fig.4. 3. Excess air control in a superheater ............................................................................ 29 Fig.4. 4. Flue gas recirculation in a superheater ...................................................................... 29 Fig.4. 5. Gas by-pass control in a superheater ......................................................................... 30 Fig.4. 6. Adjustable burner control in a superheater ................................................................ 30
Fig.5. 1. Impulse turbine on left side vs reaction turbine on right side ................................... 32 Fig.5. 2. Schematic of a condensing turbine ............................................................................ 33 Fig.5. 3. Schematic of a non-condensing turbine .................................................................... 34 Fig.5. 4. Schematic of an extraction turbine ............................................................................ 34
Fig.6. 1. Shell and tube heat exchanger .................................................................................. 37 Fig.6. 2. Schematic of a jet condenser ..................................................................................... 38
6
Fig.6. 3. Schematic of a typical jet ejector .............................................................................. 39
Fig.7. 1. T-s diagram of simple ideal Rankine cycle ............................................................... 41 Fig.7. 2. Components of a steam turbine power plant ............................................................. 41
Fig.7. 3. Effect of lowering the condenser pressure on efficiency of Rankine cycle .............. 42 Fig.7. 4. Effect of superheating the steam to a higher temperature on efficiency of Rankine
cycle ......................................................................................................................................... 43 Fig.7. 5. Effect of increasing the boiler pressure on efficiency of Rankine cycle ................... 43
Fig.8. 1. P-v diagram of an Otto cycle ..................................................................................... 45 Fig.8. 2. A natural gas engine with generator .......................................................................... 45 Fig.8. 3. Schematic diagram of a turbocharger ........................................................................ 46 Fig.8. 4. Schematic diagram of an aftercooler attached with intake manifold ........................ 46
Fig.8. 5. Firing order of the engine .......................................................................................... 47 Fig.8. 6. Schematic of a plate type heat exchanger ................................................................. 47
Fig.9. 1. P-v and t-s diagram of diesel cycle ........................................................................... 50 Fig.9. 2. Diesel generator set ................................................................................................... 51 Fig.9. 3. Schematic diagram of a turbocharger ........................................................................ 51 Fig.9. 4. Schematic of engine cooling system ......................................................................... 52
Fig.9. 5. Schematic of diesel engine fuel injection system ...................................................... 52
Fig.10. 1. Forced draft cooling tower ...................................................................................... 54 Fig.10. 2. Induced draft cooling tower .................................................................................... 55 Fig.10. 3. Cooling tower with hybrid draft .............................................................................. 55
List of Tables Table 2. 1. Main observations table ........................................................................................ 23 Table 2. 2. Effect of of steam and fuel mass flowrates and enthalpy on thermal efficiency .. 23
Table 3. 1. Effect of pressure at inlet of calorimeter on dryness fraction of steam ................ 27
Table 4. 1. Effect of various temperatures and fuel flowrate on thermal efficiency of a
superheater ............................................................................................................................... 31
Table 5. 1. Effect of turbine inlet and outlet enthalpy; and steam flowrate on thermal
efficiency of steam turbine ....................................................................................................... 36
Table 6. 1. Effect of various temperatures and water flowrate on condenser heat exchange
rate............................................................................................................................................ 40
Table 7. 1. Effect of work output and fuel flowrate on thermal efficiency of steam power
plant.......................................................................................................................................... 44
Table 8. 1. Effect of fuel flowrate and work output on efficiency of gas generator set .......... 48
Table 9. 1. Effect of fuel flowrate and work output on thermal efficiency of diesel generator
set ............................................................................................................................................. 53
7
Table 10. 1. Effect of different temperatures on thermal efficiency of cooling tower ............ 56
List of Experiments
EXPERIMENT NO: 1
Visit to Mini Steam Turbine Power Plant (Model PC-TMS-400A)
EXPERIMENT NO: 2
To determine the thermal efficiency (ηth) of a steam boiler and measure its evaporating rate
EXPERIMENT NO: 3
To determine the dryness fraction (x) of steam with the help of throttling calorimeter
EXPERIMENT NO: 4
To determine the thermal efficiency of a super heater and evaluate its performance
EXPERIMENT NO: 5
To determine the thermal efficiency of a steam turbine and evaluate its performance
EXPERIMENT NO: 6
To determine the condenser heat exchange rate and evaluate its performance
EXPERIMENT NO: 7
To determine the overall efficiency of Steam Turbine Experimental Apparatus
EXPERIMENT NO: 8
To determine the overall efficiency of Gas generator set of UET
EXPERIMENT NO: 9
To determine the overall efficiency of Diesel generator set of UET
EXPERIMENT NO: 10
To determine the thermal efficiency of Cooling towers at UET
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1. Experiment No -1
1.1 Objective Visit to Mini Steam Turbine Power Plant (Model PC-TMS-400A)
1.2 Steam turbine power plant The diagram of the specified steam power plant is given below:
Fig.1. 1. Steam turbine power plant running on kerosene oil
1.2.1 Basic Process The thermodynamic cycle for the steam turbine is known as the Rankine cycle. This cycle is
the basis for conventional power generating stations and consists of a heat source (boiler) that
converts water to high pressure steam. In the steam cycle, water is first pumped to elevated
pressure, which is medium to high pressure, depending on the size of the unit and the
temperature to which the steam is eventually heated. It is then heated to the boiling
temperature corresponding to the pressure, boiled (heated from liquid to vapor), and then
most frequently superheated (heated to a temperature above that of boiling). The pressurized
steam is expanded to lower pressure in a turbine, then exhausted either to a condenser at
vacuum conditions, or into an intermediate temperature steam distribution system that
delivers the steam to the industrial or commercial application. The condensate from the
condenser or from the industrial steam utilization system is returned to the feedwater pump
for continuation of the cycle.
The simple Rankine cycle is shown below:
9
Fig.1. 2. T-s diagram of simple Rankine cycle
1.2.2 Types of steam turbine power plants based on efficiency improvements Following modifications are done to steam turbine power plant for improving thermal
efficiency of the cycle:
1. Super heating the dry saturated steam
2. Reheating of the steam
3. Regeneration with open and closed feedwater heater
1.2.2.1 Steam cycle with super heating In this cycle, the dry saturated steam at the boiler outlet is heated in a super heater so
that it becomes extremely hot and becomes super-heated vapor. This increases the vapor
quality at turbine outlet as well as thermal efficiency of the cycle. But it needs extra fuel
input.
➢ Steam at turbine inlet is super-heated
➢ Steam at turbine outlet is wet with high dryness fraction
Its cycle is shown below:
s
Fig.1. 3. Effect of heating the steam to a higher temperature at the turbine inlet
Its schematic is shown below:
10
Fig.1. 4. Schematic diagram of a superheater
1.2.2.2 Reheating cycle In this cycle, the steam is expanded in high pressure turbine at intermediate pressure and then
this steam goes into the reheater present inside the boiler which increases the temperature of
the steam at constant pressure. This steam goes into the low-pressure turbine to produce more
output work.
It increases the thermal efficiency of cycle but more heat input is required and the power
plant becomes more complex.
➢ Steam at turbine inlet is super-heated
➢ Steam at turbine outlet is wet with high dryness fraction
Reheat cycle is given below:
Fig.1. 5. Rankine cycle with reheating of the steam
Its schematic plant layout is shown below:
11
Fig.1. 6. Schematic diagram of the steam power plant with a reheater
1.2.2.3 Regenerative cycle In this cycle, the steam passing through steam turbine is bleeded at an intermediate stage and
it passes through the feedwater heater to heat the feed water coming from condenser.
In open feed water heater, the steam and feedwater directly mix while in closed feedwater
heater there is no direct contact.
This modification increases the thermal efficiency of the cycle, but plant becomes more
complex and difficult to maintain.
➢ Steam at turbine inlet is super-heated
➢ Steam at turbine outlet is wet with dryness fraction less than in reheat cycle
Cycle with open feedwater heater and its schematic is shown below:
Fig.1. 7. Schematic of steam power plant with regeneration using open feedwater heater and
its T-s cycle
Cycle with closed feedwater heater and its schematic is shown below:
12
Fig.1.8. Schematic diagram of steam power plant with regeneration using closed feedwater
heater and its T-s cycle
1.2.3 Components A schematic representation of a steam turbine power plant is shown below:
Fig.1. 9. Components of a steam turbine power plant
In the simple schematic shown, a fuel boiler produces steam which is expanded in the steam
turbine to produce power. When the system is designed for power generation only, such as in
a large utility power system, the steam is exhausted from the turbine at the lowest practical
pressure, using a water-cooled condenser to extract the maximum amount of energy from the
steam.
13
14
2. Experiment No -2
2.1 Objective To determine the thermal efficiency (ηth) of a steam boiler and measure the
evaporating rate
2.2 Apparatus Boiler (Steam generating device)
2.3 Theory
2.3.1 Boiler It is the component in which water is converted to steam by combusting the fuel. The phase
change process occurs in the evaporator part of the boiler at constant elevated pressure so that
more heat can be added to the water. Inside a boiler, there may be an economizer which
preheats the water by waste flue gases. The superheater present in the boiler heats up the dry
saturated steam. There are various types of fuels for running boiler, but coal is used
commonly.
2.3.1.1 Types of fuel used in boiler
2.3.1.1.1 Fuel oil boiler It runs on the fuel oil like diesel and residual fuel. They are very diverse. They are used for
both industrial and residential purposes.
2.3.1.1.2 Propane boiler This runs on the propane gas which is a byproduct of natural gas.
2.3.1.1.3 Natural gas boiler This boiler uses natural gas to produce steam. These are mostly used for domestic purposes.
2.3.1.1.4 Electric boiler These boilers use electric heater for steam production. These are very efficient and there is no
waste gas.
2.3.1.1.5 Biofuel boiler This boiler uses wood and other biofuels for steam production. These are least expensive but
mostly used for domestic purposes.
2.3.1.1.6 Nuclear boiler These boilers use nuclear fuel like Uranium or Plutonium for carrying out nuclear fission
reaction and the heat released causes the water to boil.
There are some health hazards due to radiation emission and nuclear waste needs to be
disposed off properly to save the environment.
2.3.1.1.7 Coal boiler This is the most commonly used boiler for power plants because of availability of coal and
cheap price. But it affects environment by the carbon emissions.
2.3.1.1.8 Boilers running on renewable energy Renewable energy like solar and wind are used for steam generation and there is no effect on
environment since there are no emissions and this energy is renewable and abundantly
available.
2.3.1.2 Type of boilers There are various bases upon which boilers are classified, which are given below:
15
2.3.1.2.1 According to Relative Passage of water and hot gases
1. Water Tube Boiler: A boiler in which the water flows through some small tubes
which are surrounded by hot combustion gases, e.g., Babcock and Wilcox,
Stirling, Benson boilers, etc.
Following diagram shows this type:
Fig.2. 1. Schematic of a water tube boiler
2. Fire-tube Boiler: The hot combustion gases pass through the boiler tubes, which
are surrounded by water, e.g., Lancashire, Cochran, locomotive boilers, etc.
Following diagram depicts this type:
Fig.2. 2. Schematic of a fire tube boiler
2.3.1.2.2 According to Water Circulation Arrangement 1. Natural Circulation: Water circulates in the boiler due to density difference of
hot and water, e.g., Babcock and Wilcox boilers, Lancashire boilers, Cochran,
locomotive boilers, etc.
2. Forced Circulation: A water pump forces the water along its path, therefore, the
steam generation rate increases, Eg: Benson, La Mont, Velox boilers, etc.
Following figure explains these types:
16
Fig.2. 3. Forced water circulation vs natural water circulation in a boiler
2.3.1.2.3 According to the Use 1. Stationary Boiler: These boilers are used for power plants or to process steam
in plants. Following figure depicts it:
Fig.2. 4. A stationary boiler
2. Portable Boiler: These are small units of mobile and are used for temporary
uses at the sites. Following figure depicts it:
17
Fig.2. 5. A portable boiler
3. Locomotive: These are specially designed boilers. They produce steam to drive
railway engines. Following figure depicts it:
Fig.2. 6. Use of the boiler in locomotive
4. Marine Boiler: These are used on ships.
Following figure depicts this type:
18
Fig.2. 7. Schematic diagram of the boilers under operation in a ship
2.3.1.2.4 According to Position of the Boilers 1. Horizontal
Fig.2. 8. A boiler in horizontal position
2. Inclined
Fig.2. 9. A boiler with inclined water tubes
19
3. Vertical boilers
Fig.2. 10. A boiler with vertical fire tubes
2.3.1.2.5 According to the Position of Furnace 1. Internally fired: The furnace is located inside the shell, e.g., Cochran,
Lancashire boilers, etc.
Following figure depicts this:
2. Externally fired: The furnace is located outside the boiler shell, e.g., Babcock
and Wilcox, Stirling boilers, etc.
Following figure depicts these:
Fig.2. 11. Schematic of internally fired boiler on left side vs externally fired boiler on right
side
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2.3.1.2.6 According to Pressure of steam generated 1. Low-pressure boiler: a boiler which produces steam at a pressure of 15-20 bar
is called a low-pressure boiler. This steam is used for process heating.
2. Medium-pressure boiler: It has a working pressure of steam from 20 bars to 80
bars and is used for power generation or combined use of power generation and
process heating.
3. High-pressure boiler: It produces steam at a pressure of more than 80 bars.
4. Sub-critical boiler: If a boiler produces steam at a pressure which is less than
the critical pressure, it is called as a subcritical boiler.
5. Supercritical boiler: These boilers provide steam at a pressure greater than the
critical pressure. These boilers do not have an evaporator and the water directly
flashes into steam, and thus they are called once through boilers.
Difference in Rankine cycle of super and subcritical boiler is shown below:
Fig.2. 12. T-s diagram of supercritical and subcritical Rankine cycle
2.3.1.2.7 According to charge in the furnace 1. Pulverized fuel (powdered coal is used)
It is shown in Fig.2. 13.
21
Fig.2. 13. Boiler running on pulverized coal
2. Supercharged fuel (compressed air is used)
It is shown below:
Fig.2. 14. Steam cycle with supercharged boiler
22
3. Fluidized bed combustion boilers (air is passed through the fluidized bed of fuel)
It is shown below:
Fig.2. 15. Boiler using fluidized bed of coal and limestone for steam production
2.4 Specification
Maximum Pressure 10 kg/cm2
Equivalent evaporative quantity 150kg/h
Heat transmission area 3.06 m2
Rated heat out put 80,850 kcal/h
Potential water quantity 54 L
Fuel consumption 10.8 L/h (kerosene oil)
Fuel tank 90 L
Pressure gauge 15 kg/cm2
2.5 Procedure
2.5.1 Boiler Starting up Open water Supply valve. Turn main power ON. Open air purging valve. Open
drain valve. After total blow-off, close drain valve and air purging valve. Open
fuel valve and press feed water switch. Press combustion switch.
Steam pressure goes up and when it gets set value, combustion stops
automatically. Open main steam valve gradually. Note feed water inlet
23
temperature from panel and note pressure of generated steam from the outlet
pressure gauge. Note the volume of feed water fed to the boiler and fuel consumed
in specific time interval, from integral flow meters on control panel, to determine
their volume flow rates.
2.6 Specimen Calculation
Thermal efficiency of the boiler is given by
ηth = ms(h1-h6)/mf x C.V
where
ms = mass flow rate of steam generated =ρw Vw / t
mf = mass flow rate of fuel consumed = ρf Vf / t
C V = 42700(kj/kg)
ρf = 820 kg/m3
ηth = 0.0134(2682.85 – 89.8)/0.0011 x 42700
ηth = 74.1%
2.7 Observations
Table 2. 1. Main observations table
No of
Obs.
p1
(bar)
T6
(ºC)
Dryness
fraction
x
Vw
(L)
Vf
(L)
t
(sec)
1
2
3
4
Table 2. 2. Effect of of steam and fuel mass flowrates and enthalpy on thermal efficiency
ms
(kg/s)
mf
(kg/s)
h1
(kj/kg)
h6
(kj/kg)
ηt
(%)
24
25
3. Experiment No – 3
3.1 Objective To determine the Dryness Fraction of steam (x) with the help of Throttling
calorimeter.
3.2 Apparatus Steam generating device
Throttling calorimeter.
3.3 Theory
3.3.1 Dryness fraction/ quality of steam ➢ It is the ratio of vapor mass to total (vapor and water liquid) mass of steam
➢ Dry saturated steam has no liquid content i.e., no wetness
➢ Wet steam has some vapor as well as liquid water content
3.3.2 Throttling process & throttling calorimeter
3.3.2.1 Throttling process The temperature change of a gas or liquid when it is forced through a valve or porous plug
while kept insulated so that no heat is exchanged with the environment. This procedure is
called a Throttling process.
In this process here is no change in enthalpy from state one to state two, h1 = h2; no work is
done, W = 0; and the process is adiabatic, Q = 0.
We can observe that: Pin > Pout, velin < velout (where P = pressure and vel = velocity).
These observations confirm the theory that hin = hout. In this process, steam becomes drier and nearly saturated steam becomes, superheated.
3.3.2.2 Throttling calorimeter It consists a narrow throat (Orifice). Pressure and temperature are measured by pressure
gauge and thermometer. The steam after throttling process passes through the heat exchanger
and condensate is collected.
It is a vessel with a needle valve fitted on the inlet side. The steam is throttled through the
needle valve and exhausted to the condenser.
It is shown below:
Fig.3. 1. Schematic of a throttling calorimeter
26
The throttling process on Mollier chart and T-s diagram is shown below:
Fig.3. 2. Throttling process on t-s and h-s chart
3.4 Specifications Pressure gauge 10kg/cm2, 2kg/cm2
Throttle type Needle Valve type
3.5 Procedure
Open needle valve to induce steam to the throttling calorimeter. Then reduce the
pressure after expansion by means of needle valve and valve down to designated pressure.
‘Designated pressure’ means the value where the steam becomes superheated steam in
combination with the temperature after the throttle. After the temperature becomes steady,
note the pressure before and after the throttle on the respective pressure gauge and note the
temperature of outlet superheated steam.
3.6 Specimen Calculation Dryness fraction = mg/mg + mf
For throttling h1 = h2
h1 = hf1 + x hfg1
h2 = h ( at p2 , T2 ) from superheated steam table
x = (h2-hf1)/hfg1
= (2682.85– 730.213) / 2025.71
x = 0.964
27
3.7 Observations
Table 3. 1. Effect of pressure at inlet of calorimeter on dryness fraction of steam
No. of
obs
p1
(bar)
p2
(bar)
T2
( ºC )
h1 = h2
( kj/kg)
x
1
2
3
4
28
4. Experiment No - 4
4.1 Objective To determine the efficiency of superheater and evaluate its performance
4.2 Apparatus Steam Super Heater
4.3 Theory
4.3.1 Superheater A superheater is present inside boiler. When the steam leaves the evaporator then it passes
through the superheater tubes which further heats up the saturated steam to increase its
temperature at constant pressure.
The general working principle of superheater is that heat generated by fuel which changes
phase of feedwater also increases the temperature of the saturated steam or there may be
additional supply of fuel for superheater as shown:
Fig.4. 1. Schematic diagram of a superheater present inside boiler
And the separate fuel supply is shown below:
Fig.4. 2. Schematic diagram of a superheater with separate fuel supply
4.3.1.1 Control methods of superheater For temperature control of superheated steam, we have following methods:
29
4.3.1.1.1 Excess Air Control The steam outlet temperature of a convection superheater may be increased at partial load by
increasing the excess air supply. The reduced gas temperature decreases the furnace heat
absorption for the same steam production. The increased gas mass flow with its increased
total heat content serves to increase the degree of superheat.
Fig.4. 3. Excess air control in a superheater
4.3.1.1.2 Flue Gas Recirculation The recirculation of some percentage of the combustion gases serves to control steam
temperature in the same manner as does an increase in excess air. By introducing the hot
gases below the combustion zone, relatively high efficiency may be maintained.
Fig.4. 4. Flue gas recirculation in a superheater
30
4.3.1.1.3 Gas By-pass Control The boiler convection banks can be arranged in such a manner that portion of the gases can
be by-passed around the superheater elements. The superheater is oversized so that it will
produce the required degree of superheat at partial load conditions. As the load increases,
some of the flue gases are by-passed.
Fig.4. 5. Gas by-pass control in a superheater
4.3.1.1.4 Adjustable Burner Control With a multiple burner furnace, it is possible to distribute the burners over a considerable
burner wall height. This control is obtained by selective firing.
Tilt able furnace may be adjusted to shift the position of the combustion zone.
Fig.4. 6. Adjustable burner control in a superheater
31
4.4 Specifications
Inlet Pressure & Temperature 5kg/cm2 , Saturated Steam 158 ºC
Outlet Temperature 250ºC
Fuel Kerosene Oil
Pressure gauge 15kg/cm2
4.5 Procedure Close respective valves of super heater and wait for steam generation from steam.
Induce steam which goes up to designated pressure by opening valve of super heater
inlet. Open drain valve of super heater. After drained thoroughly and steam comes
out, close drain valve. Turn power switch ON. Burner starts function and steam is
super heated. Note the readings of pressure and temperature before and after the
superheater. note the reading of the volume of the fuel consumed in superheater by
the integral flow meter on the panel.
4.6 Calculations
ηth = ms (h3-h2) / mf x CV
= 43.8(2818.7 – 2758) / 0.44 x 42700
= 14.1%
4.7 Observations
Table 4. 1. Effect of various temperatures and fuel flowrate on thermal efficiency of a
superheater
No.
of
obs
P3
(bar)
p2
(bars)
T2
(ºC)
ms
(Kg/s)
T3
(ºC)
mf
(kg/h)
x
h2
(kj/kg)
h3
(kj/kg)
ηth
(%)
1
2
3
4
32
5. Experiment No – 5
5.1 Objective To determine the thermal efficiency of a steam turbine and evaluate its performance
5.2 Apparatus Steam turbine.
5.3 Theory
5.3.1 Steam turbine In the steam turbine, the steam is expanded to a lower pressure providing shaft power to drive
a generator or run a mechanical process.
There are two basic types of steam turbine according to blade design:
1. Impulse turbine
In this type, steam at high velocity hits the turbine blades and
rotates the turbine
2. Reaction turbine
In this type, steam passes through the blades which are designed
like air foil and there is pressure difference between 2 sides of the blade and this causes the
shaft to rotate.
Their detail is given below:
➢ The difference between these two designs is shown in following figure:
Fig.5. 1. Impulse turbine on left side vs reaction turbine on right side
➢ In Impulse turbines, the steam jets are directed at the turbine's bucket shaped rotor
blades where the pressure exerted by the jets causes the rotor to rotate and the velocity
of the steam to reduce as it imparts its kinetic energy to the blades. The next series of
fixed blades reverses the direction of the steam before it passes to the second row of
moving blades.
➢ In Reaction turbines, the rotor blades of the reaction turbine are shaped more like
airfoils, arranged such that the cross section of the chambers formed between the
33
fixed blades diminishes from the inlet side towards the exhaust side of the blades. The
chambers between the rotor blades essentially form nozzles so that as the steam
progresses through the chambers its velocity increases while at the same time its
pressure decreases, just as in the nozzles formed by the fixed blades.
➢ The stationary nozzles accelerate the steam to high velocity by expanding it to lower
pressure. A rotating bladed disc changes the direction of the steam flow, thereby
creating a force on the blades that, because of the wheeled geometry, manifests itself
as torque on the shaft on which the bladed wheel is mounted. The combination of
torque and speed is the output power of the turbine. A reduction gear may be utilized
to reduce the speed of the turbine to the required output speed for the generator.
➢ The internal flow passages of a steam turbine are very similar to those of the
expansion section of a gas turbine. The main differences are gas density, molecular
weight, isentropic expansion coefficient, and to a lesser extent, the viscosity of the
two fluids.
➢ Compared to reciprocating steam engines of comparable size, steam turbines rotate at
much higher rotational speeds, which contribute to their lower cost per unit of power
developed. In addition, the inlet and exhaust valves in reciprocating steam engines
cause steam pressure losses that don’t contribute to power output. Such losses do not
occur in steam turbines. Because of these design differences, steam turbines are more
efficient than reciprocating steam engines operating from the steam at the same inlet
conditions and exhausting into the same steam exhaust systems.
5.3.1.1 Condensing turbine This power-only utility turbine exhaust directly to condensers that maintain vacuum
conditions at the discharge of the turbine. An array of tubes, cooled by water from a river,
lake or cooling tower, condenses the steam into (liquid) water. The vacuum conditions in the
condenser are caused by the near ambient cooling water causing condensation of the steam
turbine exhaust steam in the condenser.
It is shown below:
Fig.5. 2. Schematic of a condensing turbine
34
5.3.1.2 Non-Condensing turbine A non-condensing turbine (also referred to as a back-pressure turbine) exhausts some or all
its steam flow to the industrial process or facility steam mains at conditions close to the
process heat requirements, as shown below:
Fig.5. 3. Schematic of a non-condensing turbine
5.3.1.3 Extraction turbine An extraction turbine has one or more openings in its casing for extraction of a portion of the
steam at some intermediate pressure. The extracted steam may be used for process purposes,
or for feedwater heating, as is the case in most utility power plants. The rest of the steam can
be expanded to below atmospheric pressure to a condenser, or delivered to a low-pressure
steam application as illustrated below:
Fig.5. 4. Schematic of an extraction turbine
35
5.3.1.4 Material of turbine blades A major problem involved in turbine design is reducing the creep experienced by the blades
(the tendency of a material to deform under the influence of stresses with time). Because of
the high temperatures and high stresses of operation, steam turbine materials become
damaged in course of time. To limit creep, thermal coatings and superalloys with grain
boundary strengthening are used in blade designs.
Protective coatings are used to reduce the thermal damage and to limit oxidation. These
coatings are often stabilized zirconium dioxide-based ceramics. Using a thermal protective
coating limits the temperature exposure of the nickel superalloy. This reduces the creep on
the blades. Oxidation coatings limit efficiency losses caused by a buildup on the outside of
the blades, which is especially important in the high-temperature environment.
The nickel-based blades are alloyed with aluminum and titanium to improve strength and
creep resistance. The microstructure of these alloys is composed of different regions of
composition.
Refractory elements such as rhenium and ruthenium can be added to the alloy to improve
creep strength. The addition of these elements reduces the diffusion of the gamma prime
phase, thus preserving the fatigue resistance, strength, and creep resistance.
Different grades of stainless steel are also used in steam turbines when the temperature of
steam is limited to 620°C.
5.4 Specification
Out Put Maximum 0.6 kW
Rotational Speed 3000 rpm
Governor Electro magnetic rotational speed
detector Digital PID Controller
Inlet/outlet Pressure gauge 10 kg/cm2, 5 kg/Cm2
5.5 Procedure Start boiler and set steam pressure to the turbine by means of reducing valves.
The designed steam condition of turbine is approximately 5kg /cm2 G (read value on a
pressure gauge) 200 ºC of superheated steam. Turbine out put can be obtained by
varying the generators load resistance. But, at that time, do not set steam pressure higher
than 8kg/cm2. And steam flow must not be more than 120kg/hr. Note the readings of
the turbine inlet pressure and temperature, turbine outlet pressure and temperature,
voltage and current of the generator
5.6 Specimen Calculation
ηt = V I/ ηg ms(hin - hout)
= 0.107 / 0.517 x 0.1216(2739.4 – 2711)
= 59.6%
36
5.7 Observations
Table 5. 1. Effect of turbine inlet and outlet enthalpy; and steam flowrate on thermal
efficiency of steam turbine
No of
obs
pin
(bar)
Tin
(ºC)
hin
(kj/kg)
Pout
( bar)
Tout
(ºC)
hout
(kj/kg)
ms
(kg/s)
VI
( kw)
ηg
(%)
ηt
(%)
1
2
3
4
37
6. Experiment No - 6
6.1 Objective To determine the Condenser heat exchange rate and evaluate its performance
6.2 Apparatus Condenser heat exchanger
6.3 Theory
6.3.1 Condenser It is a heat exchanger that removes heat from the steam at the turbine outlet and changes the
steam to saturated water.
Following are the purposes of using condenser:
1. To keep the low back pressure at turbine outlet so as to rise turbine work output
2. To reduce the volume of expanded steam at turbine outlet
6.3.1.1 Types of condenser and their construction There are two primary types of condensers that can be used in a power plant:
1. Direct Contact
2. Surface
Direct contact condensers condense the turbine exhaust steam by mixing it directly with cooling
water.
Steam surface condensers are the most commonly used condensers in modern power plants. The
exhaust steam from the turbine flows on the shell side (under vacuum) of the condenser, while the
plant’s circulating water flows in the tube side. The source of the circulating water can be either a
closed-loop (i.e. cooling tower, spray pond, etc.) or once through (i.e. from a lake, ocean, or river).
The condensed steam from the turbine, called condensate, is collected in the bottom of the condenser,
which is called a hotwell. The condensate is then pumped back to the steam generator to repeat the
cycle.
A typical surface condenser is shown below:
Fig.6. 1. Shell and tube heat exchanger
38
A jet condenser which is a direct contact condenser is shown below:
Fig.6. 2. Schematic of a jet condenser
6.3.1.2 Condenser components and their functions
6.3.1.2.1 Shell The shell is the condenser's outermost body and contains the heat exchanger tubes. The shell
is fabricated from carbon steel plates and is stiffened as needed to provide rigidity for the
shell. When required by the selected design, intermediate plates are installed to serve as
baffle plates that provide the desired flow path of the condensing steam. The plates also
provide support that help prevent sagging of long tube lengths.
For most water-cooled surface condensers, the shell is under vacuum during normal operating
conditions.
6.3.1.2.2 Hotwell At the bottom of the shell, where the condensate collects, an outlet is installed. In some
designs, a sump (often referred to as the hotwell) is provided. Condensate is pumped from the
outlet or the hotwell for reuse as boiler feedwater.
6.3.1.2.3 Vaccum system For a steam ejector, the motive fluid is steam.
For water-cooled surface condensers, the shell's internal vacuum is most commonly supplied by and
maintained by an external steam jet ejector system. Such an ejector system uses steam as the motive
fluid to remove any non-condensable gases that may be present in the surface condenser. The Venturi
effect, which is a particular case of Bernoulli's principle, applies to the operation of steam jet ejectors.
Motor driven mechanical vacuum pumps, such as the liquid ring type, are also popular for this
service.
A typical ejector is shown below:
39
Fig.6. 3. Schematic of a typical jet ejector
6.3.1.2.4 Tube sheets At each end of the shell, a sheet of sufficient thickness usually made of stainless steel is
provided, with holes for the tubes to be inserted and rolled. The inlet end of each tube is also
bell mouthed for streamlined entry of water. This is to avoid eddies at the inlet of each tube
giving rise to erosion, and to reduce flow friction. Some makers also recommend plastic
inserts at the entry of tubes to avoid eddies eroding the inlet end. In smaller units some
manufacturers use ferrules to seal the tube ends instead of rolling. To take care of length wise
expansion of tubes some designs have expansion joint between the shell and the tube sheet
allowing the latter to move longitudinally. In smaller units some sag is given to the tubes to
take care of tube expansion with both end water boxes fixed rigidly to the shell.
6.3.1.2.5 Tubes Generally, the tubes are made of stainless steel, copper alloys such as brass or bronze, cupro
nickel, or titanium depending on several selection criteria. The use of copper bearing alloys
such as brass or cupro nickel is rare in new plants, due to environmental concerns of toxic
copper alloys. Also depending on the steam cycle water treatment for the boiler, it may be
desirable to avoid tube materials containing copper. Titanium condenser tubes are usually the
best technical choice; however, the use of titanium condenser tubes has been virtually
eliminated by the sharp increases in the costs for this material. The tube lengths range to
about 17 m for modern power plants, depending on the size of the condenser. The size chosen
is based on transportability from the manufacturers‟ site and ease of erection at the
installation site.
6.3.1.2.6 Waterboxes The tube sheet at each end with tube ends rolled, for each end of the condenser is closed by a
fabricated box cover known as a waterbox, with flanged connection to the tube sheet or condenser
shell. The waterbox is usually provided with man holes on hinged covers to allow inspection and
cleaning.
These waterboxes on inlet side will also have flanged connections for cooling water inlet butterfly
valves, small vent pipe with hand valve for air venting at higher level, and hand operated drain valve
at bottom to drain the waterbox for maintenance. Similarly, on the outlet waterbox the cooling water
connection will have large flanges, butterfly valves, vent connection also at higher level and drain
connections at lower level. Similarly, thermometer pockets are located at inlet and outlet pipes for
local measurements of cooling water temperature.
40
6.4 Specification
Type Shell and tube type
Exchange heat quantity 105,000 kcal/h
Steam flow rate 180 kg/h
Heat transmission area 1.0 m2
Water receiving tank 100L
Cooling water flow rate Screw type flow meter
6.5 Procedure Measure inlet and outlet temperature of cooling water. Measure the volume flow
rate of the cooling water from the flow meter on the control panel.
6.6 Observations
Table 6. 1. Effect of various temperatures and water flowrate on condenser heat exchange
rate
No of Obs.
Tw2
(ºC)
Tw3
(ºC)
Qw
(m3/s)
mw
(kg/s)
heat
exchange
rate
(MJ/h)
1
2
3
4
41
7. Experiment No –7
7.1 Objective To determine overall efficiency of steam power plant.
7.2 Apparatus Steam Turbine Power Plant
7.3 Theory
7.3.1 Basic Process in a steam power plant The thermodynamic cycle for the steam turbine is known as the Rankine cycle. This cycle is
the basis for conventional power generating stations and consists of a heat source (boiler) that
converts water to high pressure steam. In the steam cycle, water is first pumped to elevated
pressure, which is medium to high pressure. It is then heated to the boiling temperature
corresponding to the pressure, boiled (heated from liquid to vapor), and then most frequently
superheated (heated to a temperature above that of boiling). The pressurized steam is
expanded to lower pressure in a turbine, then exhausted either to a condenser at vacuum
conditions. The condensate from the condenser or from the industrial steam utilization system
is returned to the feedwater pump for continuation of the cycle. The simple Rankine cycle is
shown below:
Fig.7. 1. T-s diagram of simple ideal Rankine cycle
7.3.2 Basic components of a steam power plant A schematic representation of a steam turbine power plant is shown below:
Fig.7. 2. Components of a steam turbine power plant
In the simple schematic shown, a fuel boiler produces steam which is expanded in the steam
turbine to produce power. When the system is designed for power generation only, such as in
a large utility power system, the steam is exhausted from the turbine at the lowest practical
pressure, using a water-cooled condenser to extract the maximum amount of energy from the
steam.
42
7.3.3 Overall efficiency of steam power plant Overall efficiency of steam turbine power plant is the product of efficiency of all components
of the power plant.
It is given as:
ᶯ= 1-(Qout/Qin) = Wout/Qin Where Wout and Qin are shown in Fig.7. 1.
7.3.4 Efficiency improvement Following are the fundamental ways of improving efficiency by rising temp. at which heat is
added or lowering temp. at which heat is rejected.
It can be done through (super heating), (reheating) and regeneration.
Following are ways of improving efficiency of the steam turbine power plant.
7.3.4.1 Lowering the Condenser Pressure (Lowers Tlow, av) Steam exists as a saturated mixture in the condenser at the saturation temperature
corresponding to the pressure inside the condenser. Therefore, lowering the operating
pressure of the condenser automatically lower the temperature of the steam, and thus the
temperature at which heat is rejected. The effect of lowering the condenser pressure on the
Rankine cycle efficiency is illustrated in below figure:
Fig.7. 3. Effect of lowering the condenser pressure on efficiency of Rankine cycle
7.3.4.2 Superheating the Steam to High Temperatures (Increases Thigh, av) The average temperature at which heat is added to the steam can be increased without
increasing the boiler pressure by superheating the steam to high temperatures. The effect of
superheating on the performance of vapor power cycle is illustrated on a T-s diagram as
shown in Figure:
43
Fig.7. 4. Effect of superheating the steam to a higher temperature on efficiency of Rankine
cycle
7.3.4.3 Increasing the Boiler Pressure (Increases Thigh, av) The average temperature during the heat addition process is to increase the operating pressure
of the boiler, which automatically raises the temperature at which boiling take place. This, in
turn, raises the average temperature at which heat is added to the steam and thus raises the
thermal efficiency of the cycle. It is depicted below:
Fig.7. 5. Effect of increasing the boiler pressure on efficiency of Rankine cycle
44
7.4 Specifications Work Output Maximum 0.6 kW
Fuel Kerosene Oil
7.5 Specimen Calculation
ηt = Wout / mf .CV
mf = mass flow rate of fuel consumed = ρf Vf / t
C V = 42700(kj/kg)
ρf = 820 kg/m3
7.6 Observations
Table 7. 1. Effect of work output and fuel flowrate on thermal efficiency of steam power
plant
No. of
obs
Wout
(kW)
mf
(kg/s)
ηt
(%)
1
2
3
4
45
8. Experiment No – 8
8.1 Objective To determine the efficiency of Gas Generator Set of UET Power House
8.2 Apparatus Gas Generator Set of UET Power House
8.3 Theory
8.3.1 Natural gas engine This engine is a spark ignition engine that uses natural gas as a fuel. It runs on the Otto cycle
which is shown below:
Fig.8. 1. P-v diagram of an Otto cycle
Here, the mixture of air and natural gas is first drawn in the cylinder and then compression
occurs and at the end of compression, a spark ignites the fuel mixture. After this, the
expansion process occurs and then burned gases are exhausted.
The diagram of Cummins gas generator is shown below:
Fig.8. 2. A natural gas engine with generator
46
8.3.2 Turbocharger A turbocharger, is a turbine-driven forced induction device that increases an internal
combustion engine's efficiency and power output by forcing extra compressed air into the
combustion chamber. This improvement over a naturally aspirated engine's power output is
due to the fact that the compressor can force more air—and proportionately more fuel—into
the combustion chamber than atmospheric pressure alone.
It is shown below:
Fig.8. 3. Schematic diagram of a turbocharger
8.3.3 Aftercooler An intercooler is a mechanical device used to cool a gas after compression process,
Compression process increases the internal energy of the gas which in turn raises its
temperature and reduces the density. In other words intercooler is a device used in
compression process, typically a heat exchanger that removes waste heat in a gas compressor.
In this natural gas engine, the temperature of the compressed fuel mixture raises to 100°C and
it becomes less dense and to increase density of this mixture we cool the mixture with an
aftercooler. Its schematic diagram is shown below:
Fig.8. 4. Schematic diagram of an aftercooler attached with intake manifold
47
8.3.4 Firing order of the engine The firing order is the sequence of power delivery of each cylinder in a multi-cylinder
reciprocating engine. This is achieved by sparking of the spark plugs in an engine in the
correct order. A sample is shown below:
Fig.8. 5. Firing order of the engine
8.3.5 Heat exchangers These are used to remove heat from the coolant passing through engine block as well as the
from the coolant passing through aftercooler.
In this gas engine, plate type heat exchangers are used in two stages i.e., high and low
temperature. The cooling water carries heat to cooling towers and then heat is removed by
evaporative cooling.
Plate type heat exchanger is shown below:
Fig.8. 6. Schematic of a plate type heat exchanger
48
8.4 Specifications
8.4.1 Engine specifications Design: 4 cycle, V-block, turbocharged low temperature after-cooled
Bore: 159 mm (6.25 in.)
Stroke: 190 mm (7.48 in.)
Displacement: 60.3 liters (3685 in3)
Cylinder block: Cast iron, V16
Battery charging alternator: None
Starting voltage: 24 volts negative ground
Fuel system: Lean burn
Ignition system: Individual coil on plug
Air cleaner type: Dry replaceable element
Lube oil filter type(s): Full flow and bypass filters
Breather: Breather filter
8.4.2 Alternator specifications Total capacity: 3.4 MW
Design: Brushless, 4 pole, revolving field
Stator: 2/3 pitch
Rotor: Two bearing
Insulation system: Class F and H see ADS (Alternator Data Sheet) for details
Standard temperature rise: 105 °C (221 °F) Continuous @ 40 °C (104 °F) ambient
Exciter type: Permanent Magnet Generator (PMG)
Phase rotation: A (U), B (V), C (W)
Alternator cooling: Direct drive centrifugal blower fan
AC waveform: Total Harmonic Distortion (THDV) < 5% no load to full linear load, < 3%
for any single harmonic
Telephone Influence Factor (TIF): < 50 per NEMA MG1-22.43
Telephone Harmonic Factor (THF): < 3
8.5 Specimen Calculation mf = mass flow rate of fuel consumed = ρf Vf / t = 0.029 kg/s
ηt = Wout / mf .CV = 430 W / (0.029*50000) = 0.296
8.6 Observations C V = 50000 kJ/kg
ρf = 0.717 kg/m3
Table 8. 1. Effect of fuel flowrate and work output on efficiency of gas generator set
No. of
obs.
Wout /s
(W)
mf (kg/s)
ηt (%)
1
49
2
3
4
50
9. Experiment No – 9
9.1 Objective To determine the efficiency of Diesel Generator Set of UET Power House
9.2 Apparatus Diesel Generator Set of UET Power House
9.3 Theory
9.3.1 Diesel engine The Diesel engine (also known as a compression-ignition or CI engine), named after Rudolf
Diesel, is an internal combustion engine in which ignition of the fuel, which is injected into
the combustion chamber, is caused by the elevated temperature of the air in the cylinder due
to the mechanical compression (adiabatic compression).
Diesel engines work by compressing only the air. This increases the air temperature inside
the cylinder to such a high degree that atomized Diesel fuel injected into the combustion
chamber ignites spontaneously. With the fuel being injected into the air just before
combustion, the dispersion of the fuel is uneven; this is called a heterogenous air-fuel
mixture. The process of mixing air and fuel happens almost entirely during combustion, the
oxygen diffuses into the flame, which means that the Diesel engine operates with a diffusion
flame. The torque a Diesel engine produces is controlled by manipulating the air ratio; this
means, that instead of throttling the intake air, the Diesel engine relies on altering the amount
of fuel that is injected, and the air ratio is usually high.
The Diesel engine has the highest thermal efficiency (engine efficiency) of any practical
internal or external combustion engine due to its very high expansion ratio and inherent
lean burn which enables heat dissipation by the excess air.
It runs on diesel cycle as shown:
Fig.9. 1. P-v and t-s diagram of diesel cycle
Diagram of the diesel generator is given below:
51
Fig.9. 2. Diesel generator set
9.3.2 Turbocharger A turbocharger, is a turbine-driven forced induction device that increases an internal
combustion engine's efficiency and power output by forcing extra compressed air into the
combustion chamber. This improvement over a naturally aspirated engine's power output is
due to the fact that the compressor can force more air—and proportionately more fuel—into
the combustion chamber than atmospheric pressure alone.
It is shown below:
Fig.9. 3. Schematic diagram of a turbocharger
9.3.3 Engine cooling system Internal combustion engine cooling uses either air or liquid to remove the waste heat from an
internal combustion engine. For small or special purpose engines, cooling using air from the
atmosphere makes for a lightweight and relatively simple system. Watercraft can use water
52
directly from the surrounding environment to cool their engines. For water-cooled engines on
aircraft and surface vehicles, waste heat is transferred from a closed loop of water pumped
through the engine to the surrounding atmosphere by a radiator.
Engine cooling system is shown below:
Fig.9. 4. Schematic of engine cooling system
9.3.4 Diesel fuel injection system Fuel injection is the introduction of fuel in an internal combustion engine, most commonly
automotive engines, by the means of an injector.
All diesel engines use fuel injection by design.
Its schematic is shown below:
Fig.9. 5. Schematic of diesel engine fuel injection system
9.4 Specifications Fuel: Diesel
Power output: 440kW
Displacement: 15000cc
53
Aspiration: Turbocharged
Compression ratio: 17:1
Bore: 137mm
Stroke: 169 mm
Radiator: Air cooled
9.5 Specimen Calculation mf = mass flow rate of fuel consumed = ρf Vf / t =0.01 kg/s
ηt = Wout / mf .CV = 393/0.01*45500 = 86.4 %
9.6 Observations C V = 45500 kJ/kg
ρf = 830kg/m3
Table 9. 1. Effect of fuel flowrate and work output on thermal efficiency of diesel generator
set
No. of
obs.
Wout/s
(kW)
mf
(kg/s)
ηt
(%)
1
2
3
4
54
10. Experiment No –10
10.1 Objective To determine the Thermal Efficiency and Water Efficiency of Cooling Towers at
UET Power House
10.2 Apparatus Cooling Towers at UET Power House
10.3 Theory
10.3.1 Cooling tower A cooling tower extracts heat from water by evaporation. In an evaporative cooling tower, a
small portion of the water being cooled is allowed to evaporate into a moving air stream to
provide significant cooling to the rest of that water stream.
10.3.2 Working of Cooling towers When water is reused in the process, it is pumped to the top of the cooling tower and will
then flow down through plastic or wood shells, much like a honeycomb. The water will emit
heat as it is downward flowing which mixes with the above air flow, which in turn cools the
water. Part of this water will also evaporate, causing it to lose even more heat.
10.3.3 Types of cooling towers
10.3.3.1 Natural draft Natural draft towers are typically about 120 m high, depending on the differential pressure
between the cold outside air and the hot humid air on the inside of the tower as the driving
force. No fans are used.
10.3.3.2 Mechanical Draft Mechanical draft towers uses fans (one or more) through the tower. They are two different
classes:
(a) Forced draft cooling towers
(b) Induced draft cooling towers
10.3.3.3 Forced Draft The forced draft tower has the fan, basin, and piping located within the tower structure. In
this model, the fan is located at the base. There are no louvered exterior walls. Instead, the
structural steel or wood framing is covered with paneling made of aluminum, galvanized
steel, or asbestos cement boards.
It is shown below:
Fig.10. 1. Forced draft cooling tower
55
10.3.3.4 Induced Draft The induced draft tower shown in the following picture has one or more fans, located at the
top of the tower, that draw air upwards against the downward flow of water passing around
the wooden decking or packing. Since the airflow is counter to the water flow, the coolest
water at the bottom is in contact with the driest air while the warmest water at the top is in
contact with the moist air, resulting in increased heat transfer efficiency.
Fig.10. 2. Induced draft cooling tower
10.3.3.5 Hybrid Draft They are equipped with mechanical draft fans to augment airflow. Consequently, they are
also referred to as fan-assisted natural draft towers. The intent of their design is to minimize
the power required for the air movement, but to do so with the least possible stack cost
impact. Properly designed fans may need to be operated only during periods of high ambient
and peak loads.
It is shown below:
Fig.10. 3. Cooling tower with hybrid draft
56
10.4 Specimen Calculation
Water Efficiency = Desired losses / Total Losses =
Water Efficiency = Water evaporated / make-up water
10.5 Theoretical Cooling Cooling Tower Inlet Temperature – Wet Bulb Temperature = CWR – WBT = 40°C
10.6 Actual cooling Cooling Tower Inlet Temperature – Cooling Tower Outlet Temperature= CWR – CWS =
34°C
Thermal Efficiency =Actual cooling / theoretical cooling x 100
= (CWR-WBT) / (CWR – CWS) x 100 = 34/40 = 0.85*100= 85%
10.7 Observations
Table 10. 1. Effect of different temperatures on thermal efficiency of cooling tower
No. of
obs
CWR(°C)
WBT(°C)
CWS(°C)
Actual
Cooling
(°C)
Theoretical
Cooling
(°C)
Thermal
Efficiency
(%)
1
2
3
4